20 inch GE CTC166CS chassis red smearing but strong CRT

[MRX37]

Originally Posted by old_tv_nut

Do you have a different source to try, like a DVD or BluRay?

Yep. Got another converter box, a DVD player, another DVD player with S-video, and so I can use this TV with a more modern source, I have an HDMI to S-video converter coming in the mail.

Originally Posted by zeno

Another thought.... IIRC the jungle IC in these was a Toshiba
TA8680. They were VERY high failure mostly for bad audio & AFT
problems.

I doubt it's the jungle IC because the customer controls work, and the smearing is slight. Frankly if it's the jungle IC then I'll just leave it alone. I've changed one of those IC's before. It is not fun. It is tedious, and I have lifted up solder traces before.

[Findm-Keepm]

Not exactly germane, but C4502 is a problem child as well. Might be well off replacing it. See the various symptom/cures in the PDF. The RCA listing for the CTC166 is 3 pages. Hope it helps.

Cheers,

[MRX37]

Originally Posted by Findm-Keepm

Not exactly germane, but C4502 is a problem child as well. Might be well off replacing it. See the various symptom/cures in the PDF. The RCA listing for the CTC166 is 3 pages. Hope it helps.

Cheers,

Oooh. Now we're getting somewhere! I'm still waiting on the SAMS but will pull C4502 when I find where it is.

[MRX37]

So I received my HDMI to S-video converter, which is sweet because now I can hook this old TV to modern video sources, and I get to show off why I like these older Colortrak 2000 based sets:



The camera does not do it justice. Those are small fonts, readable on the TV screen, at 800x600 resolution. However you can see how smeared the icons are.

Now I did notice using a DVD player that it's not just chroma:



The smearing happens with pure luma. I can see it better than the camera can.


EDIT: I decided to snap pics of the screen at different color levels:
https://i.imgur.com/gXu9Y9E.jpg

On the left, color level all the way down, and you can see just how freaking sharp the picture is. I mean for a standard def analog TV running over S-Video, that is freaking sharp!
In the middle: Color at midpoint: Still sharp but you can see how smeared the image has become.
On the right: Color at max level. The smearing is not any worse (at least it has not extended farther which definitely tells me it's not color bleed caused by a weak CRT) but the icons have lost their definition.

[MRX37]

I think I need another way to go about this.

I have a copy of the SAMS now, and while it has given me information, it hasn't given me the info I need.


So lets try something else: What are all the things that could cause the colors to smear?

Bad CRT? I doubt it because it's plenty bright and there's a lot of headroom on the drive and bias controls.

Bad U1001 IC? I doubt that because otherwise the TV works fine. Tint works fine. Color level works fine. all menus work fine.

Bad capacitors? I have been spot checking them since I did find one that was bad. However that is the only one I have found. All the capacitors in the horizontal and vertical circuits check out. The caps around u1001 check out.

Bad component on the CRT neck board? I have seen color smearing caused by bad electrolytic capacitors on the CRT neck board before. I found one of the old CRT based iMac's that had that issue. However this RCA has no electrolytic capacitors on the CRT neck board. It does have carbon resistors, but the one I spot checked reads fine.


Don't have a CRT tester so can't test it to see if there's an issue with cutoff or maybe a short that's bleeding off the video information?

There's a thought! Yes it is almost like the color information is being bled off.

Here is what I am getting at: https://youtu.be/hC0yyphcahw

This is a video on a TV with a shorted CRT. shango066 rigged up a way to isolate the short so the TV would work, and you can see near the end of the video, when the CRT shorts it gets all smeared because the video information is bleeding off into the isolation transformer.


I don't think my CRT is shorted. If it was I doubt the TV would even turn on. However I do wonder if the reason the colors are smeared is because the color information is not fully getting through, or it's being bled off by a bad component?

[old_tv_nut]

Do you see the smear on EVERY source you have? Or, is one (the DVD?) better?

[old_tv_nut]

You could have more than one thing going on, so let's try to clarify:

1) What is the source of the menus in post #14? Is it an internal menu from the TV, or from an external device? If internal, this may be a separate problem with the menu video injection (separate from the chroma delay you see on external sources).

2)The external sources you have shown so far all seem to have the chroma delayed compared to the luma. Maybe a luma delay line problem, but I would think if it was a bad delay line, the luma frequency response/transient response would be messed up.
Some external sources may not have the luma/chroma timing adjusted to NTSC broiadcast specs, so if the luma delay is a bit short on this model of TV, it will be made worse. [NOTE: NTSC broadcast transmitter specs include an envelope delay filter to delay the luma with respect to the chroma sidebands. This was specified to match the flat sharp cutoff IF amplifiers of the original receivers. Later, manufacturers found it better to use a "haystack" IF response, which did not match the transmitter filter. This was compensated by using a slightly longer luma delay line in the receiver. This chassis may simply use a slightly short luma delay line, the effect of which is made worse by the lack of a lack of envelope delay in common sources. Unfortunately, there is no analog station on the air that you could use to check.]

3) Have you tried to see if it changes significantly with fine tuning? [Thinking IF alignment or chroma alignment could be part of the issue.]

[MRX37]

Post 14 is the TV's own menu.

This TV is from 1992. It has no fine tuning that I am aware of. Also I am running it off of S-Video which should not involve the tuner.

The luma delay line is worth exploring, but where would I find that? Luma and Chroma are controlled by a big IC.

[old_tv_nut]

This has an electronic tuner rather than mechanical, right? (So no fine tuning, just enter the channel number).

Can you check the schematic or post portions for the following:

IF: is it a surface wave filter (no or very few adjustable coils)?

Delay Line: should be a tubular coil a few inches long and a half inch or so in diameter, with the schematic symbol shown.

[MRX37]

These are gonna be pretty big images, but I wanted to make sure everything was easy to read. This is the schematic for the chassis:

https://i.imgur.com/gI8b7nb.jpg
https://i.imgur.com/FDNLSs5.jpg

I've been following it best I can and have tried tweaking the 3 coils near the IC area, to no effect.

[old_tv_nut]

If you're going to start tweaking things without any service instructions of what they do, no one can help you.

It's impossible to tell what the functions of a lot of parts are that are connected to IC pins with no explanation of what's inside.

Also, this page seems to have a lot of connections to page 4 and some to page 3. I don't see the S-video input on this page, for example.

At this stage, it's still hard to say definitively if the smears are just poor design or actually something that could be fixed.

[old_tv_nut]

Also, it's very unlikely that any coil adjustments are causing those smears. This set uses a SAW (surface acoustic wave) IF, which cannot go out of alignment. If a smear actually is due to component failure, it's likely a capacitor(s).

[MRX37]

On the subject of tweaking coils:

I try not to be stupid, and mark the original positions of any coils that I tweak, and typically I will tweak them maybe 1/2 to 3/4 of a turn in either direction just to see if there is any effect. There was none and your explanation tells me why.

So more and more I am getting the impression that I may just have to live with it. It may just be the design, or a component that has aged that I either can't find or is not worth replacing.

Unless I think of something else what I very likely will do is just keep this set and wait until I find another set of this design (Colortrak 2000, RCA Dimensia, GE Somethingorother, maybe Proscan, and compare picture quality.

If I find one of a compatible design with a tired CRT I may have a good candidate to swap in as the whole chassis is rather easy to get out and no worries about setup because the yoke assembly is all bonded to the CRT.

[JohnCT]

Originally Posted by MRX37

It may just be the design, or a component that has aged that I either can't find or is not worth replacing.

I still think the jungle IC is the culprit. As far as the 166s go, I sold them brand new, and there was zero issues with performance on this or any Indiana built RCAs.

I have a notebook going back some 30 years, and I may have written in something about these. I'll check tomorrow at work.

John

[MRX37]

Originally Posted by JohnCT

I still think the jungle IC is the culprit. As far as the 166s go, I sold them brand new, and there was zero issues with performance on this or any Indiana built RCAs.

I have a notebook going back some 30 years, and I may have written in something about these. I'll check tomorrow at work.

John

Ooh. Hope you find something. That would be neat.